## (1) + (1 + 1) + (1 + 1 + 1)…

(1) + (1 + 1) + (1 + 1 + 1) + ....... + (1 + 1 + 1 + ...... n - 1 times) = ...... A. $\Large\frac{n(n+1)}{2}$ B.…

## The sum of first five multiples of 3 is..

The sum of first five multiples of 3 is: A. 45 B. 65 C. 75 D. 90 Answer: Option A Show Answer Solution(By Apex Team) \$\begin{aligned}S_n&=[2a+(n-1)d]\times\frac{n}{2}\\ \Rightarrow S_5&=[2\times3+(5-1)3]\times\frac{5}{2}\\ \Rightarrow S_5&=[6+12]\times\frac{5}{2}\\…

## If an A.P. has a = 1, tn = 20 and sn = 399..

If an A.P. has a = 1, tn = 20 and sn = 399, then value of n is : A. 20 B. 32 C. 38 D. 40 Answer: Option…